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Integers Adding—Same Signs Two Negative Numbers Two Positive Numbers Ex.) -4 + -3 Ex.) 2 + 9 • Just add the numbers, you’ve been doing this since 2nd Grade. • Just add the numbers, and keep the negative sign. -4 + -3 = -7 2 + 9 = 11 • Illustration • Illustration + + - - - + + + + + + - - - + + + - Adding—Different Signs One number is Positive, One number is negative Ex.) 6 + -5 • Subtract the Absolute Value of the Numbers, and take the sign of the larger Absolute Value 6 + -5 = 1 Follow the steps: • Abs. Value of 6 = 6 • Abs. Value of -5 = 5 • 6-5=1 • 6 is larger than 5, so the answer is positive, because the 6 is positive • + - Remember: + - A + plus a – cancel each other out. + - + - + - Illustration + + - =0 + More Examples Ex.) -5 + 3 (Different Signs…) Ex.) -3 + -7 (Same Signs…) Visual Visual - - - - - - - - + - - + - - + - - Integer Addition Strategies • Opposite Pairs + - • A + and a – cancel each other out. • Have $/Owe $ • Think of Positive Numbers as having $, and think of Negative Numbers as owing someone $. www.wpclipart.com/money/money_bag_green.png • Number Line Walk • Put Sammie on the number line above the 1st #, then “walk” Sammie the number of space of the 2nd #. If the 2nd # is positive, walk to the RIGHT, if it is negative, walk to the LEFT. • dhardhar.files.wordpress.com/2009/08/cartoon-... Subtracting • You have been subtracting “Positive Integers” since 2nd grade Ex.) 12 - 8 = Ex.) 9 – 7 = Ex.) 53 – 22 = • KFC—Keep, Flip, Change Keep—the sign of the 1st Number Flip—the operation + becomes – Change—the sign of the 2nd Number So,… • BUT…from now on…we are going to change Subtraction to Addition by KFC Ex.) 12 – 8 becomes 12 + -8 ??What do you notice about the answer?? Subtracting—use KFC Ex.) 7 – 11= (KFC…7 + -11=) now use an addition strategy to solve. Ex.) -7 – 12= Ex.) 8 – 16= Ex.) -4 – 1= Ex.) 3 – 12= Ex.) 5 – -2= Ex.) -8 – -6= Multiplying & Dividing • The Triangle Trick Ex.) 9 × -8 = + Ex.) -28 ÷ 7= - 1. × or ÷ the numbers. 2. Cover up the Signs of the numbers. 3. The sign left over, is the sign of the answer. Ex.) -3 × -11 = Ex.) -36 ÷ -6= -